1. Field of the Invention
The present invention relates to apparatus for pressing an original useful for an image forming apparatus such as a copying machine, printer or recording apparatus. More particularly, the present invention is directed to such automatic opening and closing type of original pressing apparatus which is able to press an original against an original table in good contact state even when the original is relatively thick and which allows a manual opening and closing operation whenever it is desired.
2. Description of the Prior Art
In an image forming apparatus such as a copying machine there is usually provided a pressing plate to shade the illumination light directed to an original laid on an original table also to bring the original which may be a sheet or a book into intimate contact with the surface of the original table. Recently, for the purpose of improvement in maneuverability of such image forming apparatus, the original pressing plate sometimes has been so designed as to be opened and closed automatically. However, such automatically opening and closing pressing plate hitherto known has some disadvantages. Most of the known automatic pressing plates allow no manual operation. It is very inconvenient to the operator in particular when the wishes to operate the plate manually in an emergency. Some automatic pressing plates are known which can be opened and closed also manually when it is wished. However, such manual operation is made possible only when the operator changes over the position of the plate from that for automatic operation to a manual one by using a change-over lever or the like. See, for example, U.S. Pat. No. 3,724,949.
Also, in the known pressing apparatus there was the possibility that the operator fails to notice the fact that the pressing plate is of automatic type. In such case, the operator may open or close it manually by an unreasonable force which will result in breakdown of the apparatus.
Another disadvantage involved in the known original pressing apparatus is that the post supporting the pressing plate has to be moved up and down to press a thick original against the original table. This is not only troublesome but also makes the mechanism complicated.